Detection of confined current paths on oxide surfaces by local-conductivity atomic force microscopy with atomic resolution

TL;DR

This paper demonstrates the use of local-conductivity atomic force microscopy to achieve atomic-resolution current maps on oxide surfaces, revealing localized conductivity variations likely due to oxygen vacancies.

Contribution

It introduces a method for atomic-resolution conductivity mapping on transition metal oxides and links localized surface conductivity to oxygen vacancies using DFT analysis.

Findings

Atomic-resolution current maps of TiO₂ and SrTiO₃ surfaces.

Localized surface conductivity attributed to oxygen vacancies.

DFT suggests oxygen vacancies induce nanoscale metallic states.

Abstract

The analysis of the electronic surface properties of transition metal oxides being key materials for future nanoelectronics requires a direct characterization of the conductivity with highest spatial resolution. Using local conductivity atomic force microscopy (LC-AFM) we demonstrate the possibility of recording current maps with true atomic resolution. The application of this technique on surfaces of reduced TiO$_2$ and SrTiO$_3$ reveals that the distribution of surface conductivity has a significant localized nature. Assisted by density functional theory (DFT) we propose that the presence of oxygen vacancies in the surface layer of such materials can introduce short range disturbances of electronic structure with confinement of metallic states on the nanoscale.